Australian immigration minister Tony Burke yesterday described as horrific explosive claims that asylum seekers at one of its processing camps in Papua New Guinea are being raped and tortured.

A former official at the Manus Island facility also detailed "almost daily" self-harm and attempted suicides, while warning weapons were being accumulated in readiness for a break-out attempt.

"I've never seen human beings so destitute, so helpless and so hopeless before," Rod St George, the former head of occupational health and safety at the centre, told SBS television.

"I took the position with every intention of making the place a safer environment but it proved quite rapidly to be an impossibility."

Disgusted by what he saw, St George quit.

I've never seen human beings so destitute, so helpless and so hopeless before

His allegations come just days after it was announced that the facility would be expanded as part of a hard-line plan to send all asylum-seeker arrivals to Papua New Guinea.

St George, a former prison guard, said up to half a dozen young men were assaulted and raped by fellow inmates. Those who were sexually assaulted were sent back to the same tents as the people who raped them.

Burke said he would travel to Manus Island this week to investigate the allegations.

This article appeared in the South China Morning Post print edition as PNG refugee rape report is horrific, says minister